High RPM around 4,000 while doing 55-60 mph

There are a number of things that can cause this. However, we need to start with if there are any other shifting issues? Are there any codes?

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

The most likely cause would be the torque converter is not engaging so I imagine there should be some codes confirming this.

I believe the vehicle has an OD button. Let's just make sure that button is not pressed turning off OD or it is not flashing.

Let me know what you find and we can go from there.

Thanks